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Area forecast discussion 
National Weather Service Burlington Vermont 
1009 PM EDT Wednesday Mar 17 2010 


Synopsis... 
a weak back door cold front will move into the region late tonight 
and on Thursday...with no precipitation expected. A warm front will 
approach the region late Thursday night and move through the 
region early Friday...with no precipitation expected. 


&& 


Near term /until 6 am Thursday morning/... 
as of 1009 PM EDT Wednesday...no update planned to going forecast. 
Temperatures continue to slowly fall across the County Warning Area since sunset. Increase 
cloud cover from approaching weak frontal boundary may help to cap 
temperatures...but still plenty of room to drop as dewpts(currently in 
the 20s to l30s) show little to no increase over past several hours in 
relation to temperatures dropping. So figuring continuing drop close to 
forecasted lows. 


Previous discussion...skies will be mostly clear early 
tonight...and then become partly cloudy after midnight...as a 
weak back door cold front moves south from Canada. No 
precipitation is expected with this front...just some clouds. Have 
gone a bit warmer with min temperatures overnight as southerly 
winds will help to keep temperatures up overnight. However...if 
winds decouple in some of the sheltered valleys...then 
temperatures could be colder than forecast. 


&& 


Short term /6 am Thursday morning through Friday night/... 
as of 402 PM EDT Wednesday...a weak back door cold front will be 
over the region on Thursday...with temperatures cooler then today. 
Have used a blend of NAM MOS and GFS MOS for maximum temperatures on 
Thursday. Again...just expecting some clouds around on Thursday 
and Thursday night ... no precipitation expected. The back 
door cold front will begin to start moving northeast as a warm 
front late Thursday night and early Friday...with maximum temperatures 
approaching 60 on Friday. Have gone above MOS guidance a few 
degrees Thursday night dur to cloud cover and southerly winds 
expected. 


&& 


Long term /Saturday through Wednesday/... 
as of 320 PM EDT Wednesday...overall confidence for the period is moderate... 
although low on exact timing of strong cold front passage Sunday 
night. 


Potential for significant weather impacts...moderate. 


Long term forecast period starts off rather quiet...but continued 
extremely warm. Warm air and ridging will be in place...so it 
looks like the first day of Spring will be more like early may. 
Guidance suggesting easily low 60s area wide...but given current 
trend with guidance being a bit too cool...have nudged up 
some...so suspect middle 60s quite possible in valleys. If GFS is to 
be believed with 850mb temperatures approaching 5c...perhaps a few spots 
may touch 70f. 


Bigger differences now between GFS and European model (ecmwf) than compared to 
24hrs ago. GFS has sped up the timing of low pressure and 
associated strong cold front across the region. It shows frontal 
passage Sunday evening...while the European model (ecmwf) is holding off things 
until Monday. Have compromised between the guidance solutions... 
which is in line with previous forecasts. 


Sunday still looking to be another warm day...although exactly how 
warm will depend upon how much clouds/showers we are dealing with. 
GFS would say highs only in the 50s...slower European model (ecmwf) says another 
day well into the 60s. Split the difference...so upper 50s-lower 
60s should be common place. 


Given strength of cold front...suspect temperatures could drop 10f in 2 hours 
with its passage....a small timing error will lead to big 
temperature forecast busts Sunday night and Monday...so take those 
forecasts with a bit of a grain of salt. 


Guidance still showing strong low level southerly jet developing 
Sunday/Sunday night. Could make for some gusty winds...especially 
in Champlain and St Lawrence valleys. Still think we may be close 
to Wind Advisory conditions. 


Other issue will be the amount of precipitation. Pretty high precipitable 
waters will be tapped and brought into the system. Good news is 
that it looks like it moves through pretty quickly...so amounts 
will be limited. Think 0.50-1.00 inch of precipitation is possible. 
Recent snow survey across the region indicate that we dont have a 
lot of snow left...and more will be gone prior to the rainfall. 
Thus although we will see river rises...dont think flooding will 
be an issue. Later forecasts will fine tune that prediction. 


Winter returns for Monday and Tuesday...850mb temperatures down to 
-10 to -13c...which supports highs only in the 30s at lower 
elevations (20s up higher). A brisk northwest wind will make it 
feel colder. Residual moisture will lead to scattered snow 
showers...primarily in the higher terrain...with perhaps some minor 
accumulations. 


Model guidance now showing that the shot of cold air will be 
shorter lasting with normal temperatures for Wednesday. Lots of 
uncertainty this far out...so I stuck to guidance for Wednesday. 


&& 


Aviation /02z Thursday through Monday/... 
through 00z Friday...VFR conditions through forecast period. Sky clear 
giving way to scattered-bkn080-120 by 04z Thursday. Winds west-northwest 5-15kts through 
04z-05z then shifting west-southwest 5-10 kts as front approaches...becm west-northwest 
again during remainder of period after 12z Thursday at 5-15 kts. No 
precipitation expected. 


Outlook 00z Friday through Monday... 
00z Friday-00z sun...VFR. 00z sun-00z Monday...mainly VFR...possible MVFR in 
rain showers. Increasingly gusty surface winds. 00z Monday-00z Tuesday...MVFR with 
local IFR with rain showers. Gusty surface winds. 


&& 


Btv watches/warnings/advisories... 
Vermont...none. 
New York...none. 


&& 


$$ 
Synopsis...wgh 
near term...wgh/jn 
short term...wgh 
long term...Nash 
aviation...jn/Nash